Indiana University-Purdue University Indianapolis (IUPUI) / An analysis of longitudinal data collected about beliefs regarding colorectal cancer (CRC) screenings at three-time points was analyzed to determine whether the beliefs improved from either the Web-Based, Phone-Based, or Web + Phone interventions compared to Usual Care. A mixed linear model adjusting for baseline and controlling for covariates was used to determine the effects of the intervention; Web-Based intervention was the most efficacious in improving beliefs, and phone intervention was also efficacious for several beliefs, compared to usual care.

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The dynamic structural equation modeling (DSEM) framework incorporates hierarchical latent modeling (HLM), structural equation modeling (SEM), time series analysis (TSA), and time-varying effects modeling (TVEM) to model the dynamic relationship between latent and observed variables. To model the functional relationships between variables, a Gaussian process (GP), by definition of its covariance function(s), allows researchers to define Gaussian distributions over functions of input variables. Therefore, by incorporating GPs to model the presence of significant trend in either latent or observed variables, this dissertation explores the adequacy and performance of GPs in manipulated conditions of sample size using the flexible Bayesian analysis approach. The overall results of these Monte Carlo simulation studies showcase the ability of the multi-output GPs to properly explore the presence of trends. Also, in modeling intensive longitudinal data, GPs can be specified to properly account for trends, without generating significantly biased and imprecise estimates.

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Sense of purpose in life, or the view that one’s life has direction and is guided by overarching life aims, has been found to predict better health outcomes across the adult lifespan, including better cognitive functioning and dementia risk, physical health, and improved longevity. This research is based on multi-study replications of large longitudinal datasets, as well as intensive measurement design to examine short-term (e.g., within-day, day-to-day) and long-term (years) associations between sense of purpose and markers of cognition and health. The first project used multistate survival modeling to evaluate the role of sense of purpose on transitions across cognitive states and death and was based on two large longitudinal datasets – the Rush Memory and Aging Project (MAP) and the Health and Retirement Study (HRS). More purposeful older adults were found to have lower prospective risk of developing mild cognitive impairment (and equivalent classification in HRS), later onset of impairment, and increased likelihood of improvement in cognitive functioning following MCI classification. These results were replicated across two independent longitudinal studies with disparate samples and measurement procedures. The second project examined longitudinal associations between sense of purpose in life and allostatic load in two nationally representative samples of American (HRS) and English (English Longitudinal Study of Ageing; ELSA) adults over age 50. Blood-based biomarkers of cardiovascular, metabolic, immune, and renal function, as well as anthropometric and physical markers such as lung function were used to compute overall scores representing allostatic burden. Sense of purpose in life was associated with lower overall level of allostatic load across measurement occasions in the two samples but did not predict rate of change or within-person fluctuations in allostatic burden across time. The third study investigated daily variations in sense of purpose and associations with daily cognitive performance using an ecological momentary assessment design. Multilevel models examined within- and between-person associations between end of day sense of purpose ratings and performance on five indices of cognitive functioning. Results showed no associations between daily ratings of purposefulness and performance on five cognitive tasks across a two-week period. Taken together, these findings advance existing theory and highlight important directions for the field moving forward. / Graduate / 2023-07-29

TITLE: Work, Health and the Economy: Examining Predictors of Early Retirement Among Older Canadian Workers OBJECTIVES: To investigate the contribution of socio-demographic, health, work, and health behaviour factors to the transition from work to early non-disability retirement among older Canadian workers during a period of economic recession compared to a period of non-recession. METHODS: A systematic scoping review was conducted to identify the predictors of early retirement reported in the published literature. This study also used data from Statistics Canada’s National Population Health Survey to explore the predictors of early retirement among two prospective cohorts of older Canadian workers aged 45-64 that spanned a non-recessionary economic period in Canada (cohort 1: 1994-1999) and a period which included an economic recession (cohort 2: 2006-2010). The impact of various factors on early retirement was examined using logistic regression analyses. RESULTS: Findings from the systematic scoping review were used to construct a list of variables to explore as predictors in the model. Factors which were associated with higher transitions into early retirement included older age (cohort 1: OR=1.42; cohort 2: OR=1.31), living in Quebec (cohort 1: OR=2.26), occasional (cohort 1: OR=2.56) or regular drinking (cohort 1: OR=2.32), low job satisfaction (cohort 1: OR=3.42; cohort 2: OR=3.33), working part-time (cohort 1: OR=2.16; cohort 2: OR=2.26), and employment in public administration (cohort 1: OR=2.77). While being a woman (cohort 1: OR=0.59), immigrant (cohort 1: OR=0.57), and higher job security (cohort 1: OR=0.73) were associated with lower exits to early retirement. There were differences observed in the effects of occasional and regular drinking, and for living in Quebec, on early retirement between the two contrasting economic time periods. The comparison of the provincial effect suggested that early retirement varies to some extent with the provincial unemployment rate. CONCLUSIONS: Predictors of early retirement among older Canadian workers are multifactorial. Results suggest that factors beyond individual determinants may influence early retirement and future research is needed to better understand what aspects of the provincial context are driving retirement decisions. / Thesis / Master of Science (MSc)

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